KYIV, March 23 (Reuters) - Ukrainian President Volodymyr Zelenskiy on Thursday urged Europe to increase and speed up supplies of modern weaponry and impose tougher sanctions on Russia, saying otherwise the war could drag on for years. Is there truly any rational motivation in delays concerning modern aircraft?"Zelenskiy thanked Poland and Slovakia -- now NATO members and formerly part of the Warsaw Pact -- for agreeing to supply Soviet-built MiG aircraft that Ukrainian pilots can fly without additional training. See here for a complete list of exchanges and delays